PROJECT SUMMARY/ABSTRACT The increasing prevalence of diabetes mellitus (DM) is a major health concern. DM impairs endothelial cell function and serves as a major risk factor for adverse thrombotic events (heart attacks and strokes) leading to increased mortality in diabetic patients. Von Willebrand Factor (VWF) along with NO and prostacyclin, are key blood components, produced by the endothelium, that regulate acute atherothrombosis. Patients with diabetes mellitus, have abnormally high levels of VWF, and low levels of NO and prostacyclin, predictive for adverse atherothrombotic events. The underlying mechanisms for aberrant regulation of these endothelial derived platelet modulators, in DM remain poorly understood. After extensive screening and validation assays using cutting edge approaches we have detected and confirmed experimental results which support regulation of VWF in DM patients through an intriguing putative hyperglycemia induced miRNA pathway. These results have led to our central hypothesis that hyperglycemia induced miRNA leads to dysregulation of endothelial derived platelet modulators, contributing to increased thrombosis. We will directly address the hypothesis using three Specific Aims. Specific Aim #1 will focus on the mechanism by which hyperglycemia regulates endothelial miRNA, Aim #2 will assess the mechanism by which miRNAs regulates proteins involved in the production and secretion of VWF, NO and prostacyclin, and Aim #3 will focus on the clinical significance of these findings both at a clinical patient level and using in vivo mouse models. We have gathered a team of international leaders in VWF, miRNA and diabetes mellitus to complete these Specific Aims. In the short term we will provide molecular mechanisms for the regulation and dysregulation of DM endothelium in health and disease. In the long term we will provide novel targets to combat the increased thrombosis associated with DM.